JPS62131457A - High-output low-pressure mercury vapor lamp - Google Patents

Abstract

PURPOSE:To reduce the irregularity of light emission and prevent the blackening of the wall of a light emission tube, by housing the light emission tube in a water-cooling jacket to directly cool the outside surface of the tube with cooling water. CONSTITUTION:A light emission tube 1 is housed in a jacket through which ultraviolet rays pass. The outside surface of the tube 1 is directly cooled with cooling water. The diameter of the axially central portion l2 of the tube 1 is made smaller than that of each end portion thereof. Mercury is sealed in the tube 1 near the electrodes 3a, 3b thereof. The tube 1 is lit while being uniformly cooled with the cooling water kept at a fixed temperature of 30-50 deg.C. As a result, the mercury is uniformly evaporated and distributed in the light emission tube 1 and maintained in the same state after lighting as before it. The irregularity of light emission and the blackening of the wall of the tube 1 are thus prevented throughout the period of life thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in high-output low-pressure mercury lamps used for surface sterilization of foods, medicines, their containers, packaging materials, and the like.

[Prior Art and Problems] Conventionally, an air-cooled low-pressure mercury lamp with an input power of IW or less per electrode distance 1a++ has been used for general sterilization.

However, due to the need for mass sterilization and high-performance sterilization of foods, pharmaceuticals, their containers, packaging materials, etc., high-output low-pressure mercury lamps with an input power of about 2 to 8 W per electrode distance of 1Ii1a11 have recently been used. Ta.

As an example of such a low-pressure mercury lamp, a low-pressure mercury lamp has been proposed in which a quartz arc tube that emits ultraviolet rays is housed in an ultraviolet-transparent water cooling jacket, and the outer surface of the arc tube is directly cooled with cooling water.

However, a low-pressure mercury lamp with such a configuration has the drawback that uneven light emission and early blackening of the arc tube wall are likely to occur during lighting. Among the above-mentioned drawbacks, uneven light emission is thought to occur in the following manner. In other words, when a discharge lamp is turned on, due to the initial distribution of mercury within the arc tube,
In the areas where mercury was present, the mercury emitted light was large, but in the areas where mercury was not present, the discharge occurred in an atmosphere of only the rare gas, resulting in uneven light emission as a whole. This uneven luminescence will not occur if the mercury is uniformly distributed within the arc tube from the beginning, but since mercury has the property of becoming granular due to surface tension, when filling the mercury, it is distributed evenly within the arc tube. It is difficult to do so.

Further, early blackening of the wall of the arc tube is caused by the absence of mercury around the electrodes. That is, in such a case, the discharge in the area around the electrode is a discharge of only rare gas, and as a result, the electrode material is violently scattered and attached to the wall of the arc tube. As this phenomenon progresses, the starting voltage of the discharge lamp increases, and eventually the lamp cannot be lit. Furthermore, even if mercury is uniformly distributed in the arc tube at the beginning, it will migrate to the coldest part during the lighting period, and from the time the lighting time exceeds 100 hours,
Mercury collects in the center of the arc tube and begins to cause uneven light emission due to the reasons described above.

[Purpose of the invention] The present invention has been made in view of the above points.

It is an object of the present invention to provide a high-output, low-pressure mercury lamp that exhibits less uneven light emission over the entire arc tube throughout the lighting period, less blackening of the arc tube wall, and less deterioration of ultraviolet output.

[Structure and operation of the invention]

The present invention relates to a low-pressure mercury lamp in which an arc tube is housed in a water cooling jacket and the outer surface of the arc tube is directly cooled with cooling water.

Hereinafter, the structure of the high-output low-pressure mercury lamp according to the present invention will be explained while comparing it with that of a conventional high-output low-pressure mercury lamp.

FIG. 1 is a sectional view of a conventional high-output low-pressure mercury lamp.

In the figure, reference numeral 1 denotes an arc tube of a low-pressure mercury lamp that emits ultraviolet rays, and electrodes 3a and 3b are sealed at both ends of the lamp, and an appropriate amount of mercury 6 and a rare gas are sealed inside. The arc tube 1 is housed in a water cooling jacket 2 that transmits ultraviolet light, and is configured so that its outer surface is directly cooled with cooling water 4. In such a mercury lamp, the mercury 6 sealed in the arc tube 1 is unevenly distributed in the arc tube, partly in the form of large particles and partly in the form of fine particles, as shown in the figure.

When such a discharge lamp is lit, in parts B and D of the arc tube 1 where mercury is present, I
It exhibits the appearance of a low-pressure mercury lamp under a mercury vapor pressure of rr to I X 1O-3 Torr. On the other hand, in parts A and 0, since there is no mercury supplied, the lamps exhibit the appearance of a low-pressure discharge lamp filled with only a rare gas. If the lamp continues to be lit, parts A and D, where the electrodes 3a and 3b are present, will become high in temperature, and part B will also become high in temperature due to the mercury arc, and the mercury in the arc tube will not gradually diffuse to part 0. Even if a small amount of mercury is present in the area, the mercury will actually decrease.

Also, as a phenomenon in section D, light emission of mercury is seen due to the presence of mercury grains in the initial stage, but during lighting, the temperature increases due to the heat from electrode 3b, and the temperature rises to section B and section 0, which are relatively low in temperature. When movement occurs and the lighting time exceeds 100 hours, mercury particles are no longer observed in section D, and the lamp appears to be a low-pressure discharge lamp filled only with rare gas.

In this way, if mercury becomes insufficient in parts A and D where the electrodes are located, not only will uneven light emission occur, but the electrode material will scatter significantly, causing blackening of the arc tube, and furthermore, the starting voltage will increase. This results in a situation where the lamp cannot be lit.

FIG. 2 is a sectional view of the arc tube of the high-output low-pressure mercury lamp according to the present invention. As in FIG. 1, the arc tube is housed in an ultraviolet-transparent jacket, and the outer surface of the arc tube is directly cooled with cooling water. The central part of the arc tube in the tube axis direction (
12) The diameter of the arc tube is made smaller than the diameter of both ends of the arc tube, and mercury is sealed near the electrodes 3a and 3b of the arc tube 1, and the arc tube 1 is kept at a constant temperature within the range of 30°C to 50°C. By lighting the lamp while uniformly cooling it with cooling water maintained at a constant temperature, the mercury is uniformly evaporated and dispersed within the arc tube by the heat generated by the electrodes 3a, 3b and the arc, and
Even when the arc tube is turned off, mercury does not condense in the central portion (12) of the arc tube, but instead collects in the thicker diameter portions at both ends.

The reason why the ratio of the diameter d1 at both ends of the arc tube to the diameter d2 at the center of the arc tube is d = 0.75 to 0.95 d□ is to uniformly evaporate and disperse mercury within the arc tube during lighting of the arc tube. This is to make it happen. If d2<0.75 d□,
Since the inner surface of the central portion of the arc tube becomes hot, mercury vapor is not dispersed in the central portion of the arc tube even when the arc tube is lit, and the luminescence of mercury becomes significantly weaker, and the mechanical strength also decreases.

If c12>0.95d, as in the conventional case, mercury condenses in the center of the arc tube during the lighting period of the arc tube, causing uneven light emission and blackening of the wall of the arc tube.

Next, the central part of the arc tube (12) is
~1710 is because the emission intensity of the thin part is slightly lower than that of the thick parts at both ends, so if it is longer than 173, the overall radiation output will be lower, and if it is shorter than 1/10, it will be mercury. This causes the same phenomenon as in the conventional case, such as uneven light emission and blackening of the wall of the arc tube.

In order to uniformly cool the arc tube with cooling water maintained at a constant temperature within the range of 30°C to 50°C, for example, the cooling water is circulated by a circulation device and a temperature control device is installed in the middle of the circulation path. All you have to do is set it up. Also, set the temperature of the cooling water to 3.
If the temperature is less than 30°C, the mercury in the arc tube will not evaporate sufficiently and the luminous efficiency will not increase.On the other hand, if the temperature exceeds 50°C, heat loss will increase. This is because luminous efficiency decreases.

[Effects of the Invention] As is clear from the above description, in the high-output low-pressure mercury lamp according to the present invention, if mercury is initially sealed at the end of the arc tube, mercury can be uniformly dispersed and evaporated within the arc tube. It is possible to maintain the same mercury state even after the lights are turned off as before the lights were turned on.
Therefore, uneven light emission and blackening of the wall of the arc tube can be prevented throughout the life of the bulb.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional high-output low-pressure mercury lamp, and FIG. 2 is a side view of the arc tube of the high-output low-pressure mercury lamp according to the present invention.

Claims (1)

[Claims] 1. An arc tube (1) of a low-pressure mercury lamp that emits ultraviolet rays is housed in an ultraviolet-transparent water cooling jacket (2), and the outer surface of the arc tube is directly cooled with cooling water. In the low-pressure mercury lamp, the diameter of the central part (1_2) of the arc tube in the tube axis direction is made smaller than the diameter of both ends, and the arc tube is lit while being cooled uniformly with cooling water in the range of 30 to 50°C. A high-output low-pressure mercury lamp that is characterized by: 2. The central part (1) of the arc tube (1) with respect to the diameter of both ends
_2) The high-output low-pressure mercury lamp according to claim 1, wherein the ratio of the diameters of _2) to 75% to 95%. 3. The high-output low-pressure mercury lamp according to claim 1, characterized in that the length of the central portion (1_2) of the arc tube (1) is 1/3 to 1/10 of the emission length (1_1). .